A variety of semiconductor chip packages are known that provide support for an semiconductor die (e.g., integrated circuit (IC) chip) and associated bond wires, provide protection from the environment, and enable surface mounting of the die to and interconnection to a printed circuit board (PCB), typically with solder joints. For purposes of high-volume, low-cost production of chip packages, a conventional semiconductor industry practice is to etch or stamp a thin sheet of metal material to form a panel or strip which defines multiple leadframes. A single strip may be formed to include multiple 2D arrays, with each such array including a plurality of leadframes in a particular pattern. In a typical chip package manufacturing process, the integrated circuit (IC) dies are mounted and then wire bonded to respective ones of the leadframes, then an encapsulant material (or mold compound) is applied to the strip so as to encapsulate the IC dies, bond wires, and portions of each of the leadframes.
Upon the hardening of the encapsulant material, the leadframes within the strip are cut apart or singulated for producing individual chip packages. Such singulation is typically accomplished via a sawing process. In a conventional mechanical saw process, a saw blade (or dicing blade) is typically advanced along “saw streets” which extend in prescribed patterns between the leadframes to separate the leadframes from one another.
To insure that every solder joint between the leads of a package and lands on the PCB has been fully wetted by solder an option exists to enable visually inspecting if proper solder connections exist. The “wettable flank” lead design option allows for the solder to wick up the edge of the package which is needed for visual inspection because unlike traditional leaded components such as Small Outline Integrated Circuit (SOIC) and dual-in-line (DIP) packages, the solder joints of leadless packages such as Quad Flat No-Lead (QFN) packages are formed primarily underneath the package. In the wettable flank option at least one of the top corner region and a bottom corner region of the outer edge of the leads is utilized to form a recess which is sized and configured to accommodate reflowing solder therein to enable a visual solder inspection after assembly to a package substrate such as a PCB.